Certainly, using the mall technology, and probably using either of the other two technologies, it's easy to create a protective shell covering a square mile. Here are some of the more interesting questions that would be raised if someone actually tried to do this:
How many people could live there?
We'll assume that the interior of the dome is developed at an average height of 10 stories. Some buildings will be higher, while some places in the city will be parks or otherwise undeveloped, working out to an average of 10 stories. That gives the city about 280,000,000 square feet of floor space. If you assume that the average person needs about 500 square feet of living space (pretty typical in suburban America), another 500 square feet of open space for things like hallways, walkways, parks, common areas, elevators, and so on, then this city could house almost 200,000 people. However, it's likely that real estate under the dome will be extremely valuable and that people will fit into much smaller spaces than they typically do today. In other words, the space occupied per person might total only 500 square feet. That would allow the city to hold more than half a million people.
How much would it cost to build?
In today's dollars, space in a skyscraper costs something like $400 per square foot to build. The Eden greenhouses cost around of $400 per square foot too, so we'll use that number. The total cost for this project would be something on the order of $140 billion, or $250,000 per resident. That's not so unreasonable, when you think about it.
What will it cost to heat and cool this huge structure?
That's impossible to say because it depends on the type of construction, the location, and so on. However, it's interesting to note that the Mall of America doesn't have to spend money on heating, even though it's located in Minnesota. The lights and people provide plenty of heat. The problem will be cooling this massive structure, especially when the sun is shining. One way to solve this dilemma would be to locate the domed city in a very cold climate.
How will people get around?
The maximum distance between any two points in the city will be about one mile, meaning that a person can walk anywhere in a half-hour or less. Walking will be the primary, and possibly the only, means of transportation for the residents of the city. There will need to be some way to accommodate the movement of food and retail products into the city. Underground train systems or roads for trucks might be the best solution.
The thing that you come to understand after thinking about a domed city is that it's not such a far-fetched idea. There's a good chance that we will see such a city developed over the next decade or two. Finally, people will be able to plan their weekends without having to worry about the weather!